[ltp] Display unreliable - W500

Dmitry Mikhailov linux-thinkpad@linux-thinkpad.org
Thu, 07 Nov 2013 10:43:30 +0600

On 11/07/2013 06:00 AM, Wade Curry wrote:
> So the question is, does this sound like a bad CCFL tube, or does
> it sound like something else?  If it's a bad CCFL, is there a good
> tutorial on it?  Otherwise, does it even sound reparable?  I'm not
> able to pay someone else to do it, but I've got a soldering iron
> and willingness to dig in.
First of all, the required disclaimer. I'm not responsible for anyone's 
actions and the damage to equipment and human health or even death 
resulting from carelessly applying the following directions. CCFL 
backlight units use *LETHAL* 2000 volts to start up and serious 200-400 
volts is the working voltage. You have been warned.

Replacing CCFL can be a hard job but you won't know what component to 
blame: CCFL or inverter.
Get a 100% alive same-size CCFL (hard to get, easy to test) or get a 
good 17" 4:3 LCD monitor for test. 4:3 units are old and usually come 
with CCFLs, not LEDs. The length (and thus most electrical parameters) 
of your 15" 16:9 CCFL is the same as on a 17" 4:3 screen - it's 
important. Don't get anything larger - it doesn't fit for test.

Open a monitor, disconnect everything from the LCD panel. Now you got 
the bare panel with (usually four) cables protruding from the side of 
it. These cable come to backlight CCFLs - the same as on your thinkpad.

Now rich your bare thinkpad LCD panel - there are plenty of instructions 
available online including official manuals from Lenovo.

Disconnect the thinkpad's CCFL from the inverter and manage to connect 
one of your test monitor's CCFLs to it. It may involve messing with thin 
wires (by pushing them inside the CCFL connector openings and soldering 
to thinkpad's inverter).

Now power the thinkpad on and look. If a part of your test monitor 
lights up immediately upon powerup (it's ok, only a part - as it takes 
more than one CCFL to light the whole screen up) - then it's your 
original thinkpad screen CCFL at fault.

Otherwise - it's the inverter.

One more warning for those who still follow reading: playing around with 
ripped apart unprotected mains powered electronics without an isolation 
transformer is even more dangerous than everything above. You can be 

Hey, you can also take inverse test - connect  thinkpad's CCFL instead 
of one on your test monitor and look. If CCFL is faulty, the monitor 
(and your thinkpad screen) would light up for some 2 seconds and then go 
dark. Be sure that test monitor receives some picture, otherwise power 
saving kicks in and test result is inconclusive.

Best regards,
         Dmitry Mikhailov